Changeset 396

Timestamp:

Apr 9, 2006 10:37:09 AM (18 years ago)

Author:

bennylp

Message:

Added experimental code to handle QueryPerformanceCounter? leaping bug on Win32

File:

• pjproject/trunk/pjlib/src/pj/os_timestamp_win32.c (modified) (3 diffs)

pjproject/trunk/pjlib/src/pj/os_timestamp_win32.c

@@ -18 +18 @@
  */
 #include <pj/os.h>
+#include <pj/assert.h>
 #include <pj/errno.h>
+#include <pj/log.h>
 #include <windows.h>
+
+#define THIS_FILE   "os_timestamp_win32.c"
+
+
+#if 1
+#   define TRACE_(x)        PJ_LOG(3,x)
+#else
+#   define TRACE_(x)        ;
+#endif
+
+
+/////////////////////////////////////////////////////////////////////////////
 
 #if defined(PJ_TIMESTAMP_USE_RDTSC) && PJ_TIMESTAMP_USE_RDTSC!=0 && \
@@ -95 +109 @@
 }
 
+/////////////////////////////////////////////////////////////////////////////
+
+#elif defined(PJ_TIMESTAMP_WIN32_USE_SAFE_QPC) && \
+         PJ_TIMESTAMP_WIN32_USE_SAFE_QPC!=0
+
+/* Use safe QueryPerformanceCounter.
+ * This implementation has some protection against bug in KB Q274323:
+ *   Performance counter value may unexpectedly leap forward
+ *   http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q274323
+ *
+ * THIS SHOULD NOT BE USED YET AS IT DOESN'T HANDLE SYSTEM TIME
+ * CHANGE.
+ */
+
+static pj_timestamp g_ts_freq;
+static pj_timestamp g_ts_base;
+static pj_int64_t   g_time_base;
+
+PJ_DEF(pj_status_t) pj_get_timestamp(pj_timestamp *ts)
+{
+    enum { MAX_RETRY = 10 };
+    unsigned i;
+
+
+    /* pj_get_timestamp_freq() must have been called before.
+     * This is done when application called pj_init().
+     */
+    pj_assert(g_ts_freq.u64 != 0);
+
+    /* Retry QueryPerformanceCounter() until we're sure that the
+     * value returned makes sense.
+     */
+    i = 0;
+    do {
+        LARGE_INTEGER val;
+        pj_int64_t counter64, time64, diff;
+        pj_time_val time_now;
+
+        /* Retrieve the counter */
+        if (!QueryPerformanceCounter(&val))
+            return PJ_RETURN_OS_ERROR(GetLastError());
+
+        /* Regardless of the goodness of the value, we should put
+         * the counter here, because normally application wouldn't
+         * check the error result of this function.
+         */
+        ts->u64 = val.QuadPart;
+
+        /* Retrieve time */
+        pj_gettimeofday(&time_now);
+
+        /* Get the counter elapsed time in miliseconds */
+        counter64 = (val.QuadPart - g_ts_base.u64) * 1000 / g_ts_freq.u64;
+        
+        /* Get the time elapsed in miliseconds. 
+         * We don't want to use PJ_TIME_VAL_MSEC() since it's using
+         * 32bit calculation, which limits the maximum elapsed time
+         * to around 49 days only.
+         */
+        time64 = time_now.sec;
+        time64 = time64 * 1000 + time_now.msec;
+        //time64 = GetTickCount();
+
+        /* It's good if the difference between two clocks are within
+         * some compile time constant (default: 20ms, which to allow
+         * context switch happen between QueryPerformanceCounter and
+         * pj_gettimeofday()).
+         */
+        diff = (time64 - g_time_base) - counter64;
+        if (diff >= -20 && diff <= 20) {
+            /* It's good */
+            return PJ_SUCCESS;
+        }
+
+        ++i;
+
+    } while (i < MAX_RETRY);
+
+    TRACE_((THIS_FILE, "QueryPerformanceCounter returned bad value"));
+    return PJ_ETIMEDOUT;
+}
+
+static pj_status_t init_performance_counter(void)
+{
+    LARGE_INTEGER val;
+    pj_time_val time_base;
+    pj_status_t status;
+
+    /* Get the frequency */
+    if (!QueryPerformanceFrequency(&val))
+        return PJ_RETURN_OS_ERROR(GetLastError());
+
+    g_ts_freq.u64 = val.QuadPart;
+
+    /* Get the base timestamp */
+    if (!QueryPerformanceCounter(&val))
+        return PJ_RETURN_OS_ERROR(GetLastError());
+
+    g_ts_base.u64 = val.QuadPart;
+
+
+    /* Get the base time */
+    status = pj_gettimeofday(&time_base);
+    if (status != PJ_SUCCESS)
+        return status;
+
+    /* Convert time base to 64bit value in msec */
+    g_time_base = time_base.sec;
+    g_time_base  = g_time_base * 1000 + time_base.msec;
+    //g_time_base = GetTickCount();
+
+    return PJ_SUCCESS;
+}
+
+PJ_DEF(pj_status_t) pj_get_timestamp_freq(pj_timestamp *freq)
+{
+    if (g_ts_freq.u64 == 0) {
+        enum { MAX_REPEAT = 10 };
+        unsigned i;
+        pj_status_t status;
+
+        /* Make unellegant compiler happy */
+        status = 0;
+
+        /* Repeat initializing performance counter until we're sure
+         * the base timing is correct. It is possible that the system
+         * returns bad counter during this initialization!
+         */
+        for (i=0; i<MAX_REPEAT; ++i) {
+
+            pj_timestamp dummy;
+
+            /* Init base time */
+            status = init_performance_counter();
+            if (status != PJ_SUCCESS)
+                return status;
+
+            /* Try the base time */
+            status = pj_get_timestamp(&dummy);
+            if (status == PJ_SUCCESS)
+                break;
+        }
+
+        if (status != PJ_SUCCESS)
+            return status;
+    }
+
+    freq->u64 = g_ts_freq.u64;
+    return PJ_SUCCESS;
+}
+
+/////////////////////////////////////////////////////////////////////////////
+
 #else
+
 /*
  * Use QueryPerformanceCounter and QueryPerformanceFrequency.
+ * This should be the default implementation to be used on Windows.
  */
 PJ_DEF(pj_status_t) pj_get_timestamp(pj_timestamp *ts)
@@ -121 +290 @@
 }
 
+
 #endif  /* PJ_TIMESTAMP_USE_RDTSC */